1. Technical Field
The present invention relates to a projector.
2. Related Art
A projector using a laser light source has advantages, such as reduction in the size of the device, excellent color reproducibility, instantaneous lighting, and long life time of the light source. In general, laser light emitted from the laser light source is coherent light. For this reason, in this type of projector, a spot pattern, called speckle noise, caused by interference of laser light may be visually recognized on a screen. Accordingly, display quality is significantly degraded.
In the projector of the related art using the laser light source, a countermeasure for suppressing degradation of display quality due to speckle noise is used. JP-A-2009-216843 (Document 1) discloses a projection display device in which an entrance pupil image of a projection lens is greater than an exit pupil diameter of an illumination optical system, and which includes pupil matching means for rotationally moving the exit pupil image of the illumination optical system in the entrance pupil of the projection lens. “Research Study Report on Ubiquitous Laser Display in 2009” by Kazuo Kuroda and 17 others, The Japan Machinery Federation, Optoelectronics Industry and Technology Development Association, March 2010 (Document 2) describes an explanation relating to a speckle phenomenon, a speckle elimination method, and the like.
In the projection display device of Document 1, as the pupil matching means, a transparent plate which has a plurality of minute wedge-shaped portions and a motor which rotates the transparent plate are provided. Since the pupil matching means rotationally moves the exit pupil image of the illumination optical system, it is necessary to increase the size of an imaging lens or a projection lens disposed at a subsequent stage of the pupil matching means. As a result, according to the projection display device, there is a problem in that the device increases in size due to a need for a space where the pupil matching means is disposed and an increase in the size of the imaging lens or the projection lens.
Document 2 describes a prediction method of a speckle. This prediction method assumes that a pupil image has uniform illumination. However, in general, the pupil image of the projector has an illumination distribution. For this reason, it is not possible to use the prediction method of Document 2 practically.